sensors Mode-S transponder
A1CAC9
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N2140U · BOEING 777-300ER · operated by UNITED AIRLINES INC
- Hex
- A1CAC9
- Octal
- 50345311
- Decimal
- 10,603,209
- Country
- US
- Tail
- N2140U
- Type
- B77W
- Flights observed
- 149
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 4h ago
Last known position
Country allocation
The ICAO 24-bit address A1CAC9 falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States receives a permanent address from this block at the time of registration; the address stays with the airframe even if the aircraft is re-registered to a different operator within the country.
Callsign history 20 distinct
| Callsign | Airline | Flights | Last seen |
|---|---|---|---|
| UAL989 | - | 8 | 2026-07-02 |
| UAL858 | - | 8 | 2026-07-12 |
| UAL857 | - | 8 | 2026-07-11 |
| UAL951 | United Airlines | 7 | 2026-07-02 |
| UAL950 | - | 7 | 2026-07-01 |
| UAL837 | - | 6 | 2026-07-12 |
| UAL78 | - | 6 | 2026-07-09 |
| UAL190 | - | 6 | 2026-06-28 |
| UAL988 | - | 5 | 2026-07-01 |
| UAL878 | - | 5 | 2026-06-26 |
| UAL869 | - | 5 | 2026-07-13 |
| UAL862 | United Airlines | 5 | 2026-04-16 |
| UAL43 | - | 5 | 2026-07-03 |
| UAL1960 | - | 5 | 2026-07-10 |
| UAL838 | - | 4 | 2026-07-13 |
| UAL79 | - | 4 | 2026-07-06 |
| UAL200 | - | 4 | 2026-06-30 |
| UAL877 | United Airlines | 3 | 2026-04-15 |
| UAL872 | United Airlines | 3 | 2026-06-09 |
| UAL810 | United Airlines | 3 | 2026-05-23 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-13 | UAL869 | SFO → HKG | Jul 13, 21:22 UTC | Jul 14, 10:24 UTC | 13h 2m |
| 2026-07-13 | UAL869 | - | Jul 13, 21:25 UTC | Jul 13, 21:50 UTC | 25m |
| 2026-07-13 | UAL838 | - | Jul 13, 08:35 UTC | Jul 13, 17:55 UTC | 9h 20m |
| 2026-07-12 | UAL837 | SFO → NRT | Jul 12, 19:52 UTC | Jul 13, 05:59 UTC | 10h 7m |
| 2026-07-12 | UAL837 | - | Jul 12, 19:55 UTC | Jul 13, 06:05 UTC | 10h 10m |
| 2026-07-12 | UAL858 | PVG → SFO | Jul 12, 04:44 UTC | Jul 12, 15:24 UTC | 10h 40m |
| 2026-07-12 | UAL858 | PVG → SFO | Jul 12, 04:44 UTC | Jul 12, 15:12 UTC | 10h 28m |
| 2026-07-11 | UAL858 | - | Jul 11, 08:20 UTC | Jul 12, 07:01 UTC | 22h 40m |
| 2026-07-11 | UAL857 | - | Jul 11, 06:55 UTC | Jul 12, 06:15 UTC | 23h 20m |
| 2026-07-10 | UAL857 | SFO → PVG | Jul 10, 21:17 UTC | Jul 11, 09:33 UTC | 12h 16m |
| 2026-07-10 | UAL857 | - | Jul 10, 21:10 UTC | Jul 11, 08:15 UTC | 11h 5m |
| 2026-07-10 | UAL1960 | - | Jul 10, 12:05 UTC | Jul 10, 17:10 UTC | 5h 5m |
| 2026-07-10 | UAL1960 | - | Jul 10, 11:40 UTC | Jul 10, 12:00 UTC | 20m |
| 2026-07-09 | UAL78 | - | Jul 9, 08:55 UTC | Jul 9, 21:25 UTC | 12h 30m |
| 2026-07-09 | UAL78 | NRT → EWR | Jul 9, 08:51 UTC | Jul 9, 21:18 UTC | 12h 27m |
| 2026-07-08 | UAL837 | SFO → NRT | Jul 8, 20:00 UTC | Jul 9, 06:05 UTC | 10h 5m |
| 2026-07-08 | UAL1960 | - | Jul 8, 11:35 UTC | Jul 8, 16:50 UTC | 5h 15m |
| 2026-07-07 | UAL78 | NRT → EWR | Jul 7, 08:40 UTC | Jul 7, 16:15 UTC | 7h 35m |
| 2026-07-07 | UAL78 | NRT → EWR | Jul 7, 08:51 UTC | Jul 7, 20:30 UTC | 11h 39m |
| 2026-07-06 | UAL79 | EWR → NRT | Jul 6, 16:02 UTC | Jul 7, 05:14 UTC | 13h 12m |
| 2026-07-06 | UAL79 | EWR → NRT | Jul 6, 16:20 UTC | Jul 7, 05:05 UTC | 12h 45m |
| 2026-07-06 | UAL2416 | - | Jul 6, 07:45 UTC | Jul 6, 12:20 UTC | 4h 35m |
| 2026-07-05 | UAL1844 | - | Jul 5, 22:50 UTC | Jul 6, 04:20 UTC | 5h 30m |
| 2026-07-05 | UAL41 | FCO → EWR | Jul 5, 09:55 UTC | Jul 5, 18:35 UTC | 8h 40m |
| 2026-07-04 | UAL40 | EWR → FCO | Jul 4, 21:48 UTC | Jul 5, 05:00 UTC | 7h 12m |
| 2026-07-04 | UAL40 | EWR → FCO | Jul 4, 21:45 UTC | Jul 5, 05:00 UTC | 7h 15m |
| 2026-07-04 | UAL41 | FCO → EWR | Jul 4, 09:40 UTC | Jul 4, 18:25 UTC | 8h 45m |
| 2026-07-04 | UAL41 | FCO → EWR | Jul 4, 09:27 UTC | Jul 4, 18:24 UTC | 8h 57m |
| 2026-07-03 | UAL40 | EWR → FCO | Jul 3, 21:35 UTC | Jul 4, 05:05 UTC | 7h 30m |
| 2026-07-03 | UAL43 | - | Jul 3, 09:35 UTC | Jul 3, 17:55 UTC | 8h 20m |
| 2026-07-03 | UAL43 | FRA → EWR | Jul 3, 09:31 UTC | Jul 3, 17:50 UTC | 8h 19m |
| 2026-07-02 | UAL989 | - | Jul 2, 21:50 UTC | Jul 3, 04:50 UTC | 7h 0m |
| 2026-07-02 | UAL951 | BRU → IAD | Jul 2, 10:35 UTC | Jul 2, 18:45 UTC | 8h 10m |
| 2026-07-01 | UAL950 | IAD → BRU | Jul 1, 22:40 UTC | Jul 2, 05:40 UTC | 7h 0m |
| 2026-07-01 | UAL988 | FRA → IAD | Jul 1, 10:59 UTC | Jul 1, 19:21 UTC | 8h 22m |
| 2026-07-01 | UAL42 | EWR → FRA | Jul 1, 00:30 UTC | Jul 1, 07:23 UTC | 6h 53m |
| 2026-07-01 | UAL42 | - | Jul 1, 00:15 UTC | Jul 1, 01:10 UTC | 55m |
| 2026-06-30 | UAL435 | SFO → EWR | Jun 30, 15:50 UTC | Jun 30, 20:40 UTC | 4h 50m |
| 2026-06-30 | UAL1346 | - | Jun 30, 08:30 UTC | Jun 30, 12:50 UTC | 4h 20m |
| 2026-06-30 | UAL200 | - | Jun 30, 03:40 UTC | Jun 30, 04:00 UTC | 20m |
| 2026-06-29 | UAL200 | GUM → HNL | Jun 29, 21:18 UTC | Jun 30, 04:00 UTC | 6h 42m |
| 2026-06-29 | UAL201 | - | Jun 29, 00:39 UTC | Jun 29, 00:49 UTC | 10m |
| 2026-06-28 | UAL1175 | - | Jun 28, 21:04 UTC | Jun 28, 21:20 UTC | 15m |
| 2026-06-28 | UAL1175 | - | Jun 28, 16:39 UTC | Jun 28, 17:10 UTC | 30m |
| 2026-06-28 | UAL190 | - | Jun 28, 01:04 UTC | Jun 28, 12:55 UTC | 11h 50m |
| 2026-06-28 | UAL190 | MNL → SFO | Jun 28, 01:01 UTC | Jun 28, 12:54 UTC | 11h 53m |
| 2026-06-27 | UAL189 | SFO → MNL | Jun 27, 08:14 UTC | Jun 27, 21:25 UTC | 13h 10m |
| 2026-06-26 | UAL878 | HKG → SFO | Jun 26, 14:51 UTC | Jun 27, 04:23 UTC | 13h 32m |
| 2026-06-26 | UAL878 | - | Jun 26, 15:25 UTC | Jun 27, 04:24 UTC | 13h 0m |
| 2026-06-25 | UAL869 | SFO → HKG | Jun 25, 21:15 UTC | Jun 26, 10:35 UTC | 13h 20m |
About Mode-S
A Mode-S transponder code (also called an "ICAO 24-bit address" or "hex code") is a 6-character hexadecimal identifier permanently assigned to an aircraft when it's first registered. Unlike callsigns (which change with each flight) or registrations (which can change if an aircraft is sold internationally), the Mode-S address stays with the airframe for the life of the aircraft in that country.
Every ADS-B transmission from an aircraft includes its Mode-S address, making it the most reliable way to identify a specific airframe. Flight-tracking services like Apparatus use the Mode-S address as the primary key for tying position broadcasts, callsigns, and ownership records together.
Prefer a tail-number view? See the N2140U page for operator, model, and routing details .